Compositions and methods for preservation of metals



United States Patent "ice 3,136,663 COMPOSITIONS AND METHODS FOR PRESERVATION OF METALS Louis McDonald, Altadena, Califi, assignor to Kelite Corporation, Los Angeles, Calif, a corporation of California No Drawing. Filed Oct. 24, 1960, Ser. No. 64,264 15 Claims. (Cl. 148-615) This invention relates to compositions of matter and methods for their application for the preservation of metals, and has particular reference to the preservation of metals that are sensitive to atmospheres which exhibit a deleterious or corrosive attack. In addition to ferrous alloys, this includes such metals as the alloys of iron, zinc, cadmium and certain alloys of magnesium and aluminum.

It is Well known that certain ferrous alloys such as the low carbon steels of the SAE 1000 series readily form oxygen rich oxides, commonly known as rust, when exposed to moist air and atmospheres containing oxygen, acid anhydrides and other impurities such as are commonly encountered in industrial atmospheres. Other metals such as zinc develop basic carbonate deposits commonly known as white rust under similar conditions of exposure. Still other metals or alloys such as aluminum, cadmium and their alloys develop stains. Other metals such as magnesium undergo erosion under these same conditions.

The chemical treatment of sensitive metals to provide surfaces resistant to the deleterious elfects of corrosive atmospheres has for many years received scientific attention. Accordingly, many chemical treatments intended for this purpose have been developed and have been reduced to widespread commercial practice. For example, ferrous alloys have been treated with phosphoric acid compositions to provide surfaces that resist corrosion both before and after imparting organic finishes such as lacquers, paints, enamels and primers. Other chemical treatments providing similar protection have been developed for zinc, aluminum, cadmium and magnesium alloys. 7

Enhancement of the corrosionbehavior of such alloys 3,136,663 Patented June 9,- 1964 Other objects and advantages of the present invention it is believed will be readily apparent from the following detailed description of preferred embodiments thereof.

Briefly, this invention comprehends within its scope the discovery that organic seal coatings formed by the deposition of a strongly anionic polymer can be made to impart improved corrosion behavior by a treatment with a strong cationic agent such as a cetyl dimethyl ammonium chloride, other quaternary compounds, cationic amines or amphoteric reagents such as N-methyl taurine. pable of strong cationic behavior such as polyvinyl pyridine and polymerized ethylene imine can be used.

This can best be accomplished by reacting the anionic polymer with a high molecular weight cationic reagent immediately after the reaction of the organic anionic polymer seal coating component with the basic metal or inorganic conversion coating. For example, low carbon steel sheet is continuously treated with phosphatizing-anionic polymer seal composition using conventional rollercoat coating equipment whereby the sheet is conveyed through two applicator rolls over which there is flowed a phosphatizing composition embodying an anionic reactive polymer to comprise the first step in preservation of the metal. After the steel sheet or strip is conveyed from the applicator roll it is passed through a second set of applicator rollers over which is flowed the cationic reactants, then through squeegee rolls to remove the excess and finally dried with warm air to comprise the second step of the preservation reaction.

The steel thusly treated shows resistance to rusting in moist air, improved by a factor of 6 times over steel which has been treated by phosphatizing alone. The improvement in resistance to rusting is 2 to 3 times greater than steel which has been phosphatized and seal coated with an anionic polymer without subsequent cationic treatment.

beyond that imparted by water-soluble inorganic compounds reactive with the metal to provide a corrosionresistant coating, commonly termed inorganic conversion coatings, such as phosphate coatings, chromate and fluoride coatings, has been taught in applicants earlier United States Patent No. 2,885,312 and in the application for reissue thereof, Serial No. 824,759, filed July 2, 1959, now Reissue No. 24,875. This patent discloses the deposition of an organic seal coating comprised of a strongly anionic water soluble polymer compound capable of deposition on the metal or phosphatized metal surface or chromatized metal surface from an aqueous bath. It has been shown that resistance to weathering of phosphatized steel is improved by this means by a factor of the order of 2 or 3.

It is a primary object of the present invention to provide novel and improved compositions and methods for the preservation of metals.

Another object of this invention is to provide a process for imparting a corrosion-resistant coating to metals which is superior to those heretofore proposed and used.

The reaction between the anionic polymer and the cationic reagent results in the formation of a copolymer of approximately double the molecular weight of i the anionic polymer. vThese cationic agents are broadly defined as organic cationic substances having a basic nitrogen atom. In this reaction the co-polymer is rendered insoluble and more adherent to the inorganic conversion or basis metal.

The following represents a generic typical reaction which occurs between the anionic polymer and a quaternary cationic reactant:

where R is an organic grouping with a free valence such as, for example a vinyl-substituted aryl group capable of polymeric reaction, X is a strong polar group such as a sulfonic acid, carboxylic acid, or phosphonic acid Also, water soluble polymeric substances ca- "D 3 group and Y is hydrogen, metal, N is a nitrogen atom, R R R and R are alkyl,

aryl or alkyl substituted aryl groups or hydrogen atoms,

Z is a halogen ion, A is a hydrocarbonterminal group and n is an integer greater than 1. When the cationic reactant contains nitrogen with a valance of three, the

reaction with the anionic polymer may be represented by the equation:

where R, X, N, R R R Y, A and n have the mean ings given above.

It will be understood that the foregoing formulas for the cationic reactants are given merely for the purpose of the representative equations and do not embrace all of the cationic substances within the scope of the invention. Thus, as will be seen hereinafter, various heterocyclic amines, imines, imidazoles, and polymerized amines may be employed. In general, however, the cationic substances react in the manner illustrated by the equaan ammonium radical or a variety of cationic substances capable of reacting with the preferred classes of anionic polymers to produce the desired types of insoluble co-polymers. These cationic substances maybe employed in the form of monomers or in the form of polymers capable of undergoing cationic reactions. The following are cited as typical examples:

Class of cationic substances:

Acetic acid salts of allryl amines.

Salts of fatty acid tertiary amines.

Bth anolated alkyl guani dine amine complexes.

Fatty acid amines.

Alkyl hetrocyclic tertiary amines.

Alkyl dimethyl amine oxide. v

Fatty diethanol amides.

Tertiary amine ethylene oxide condensates of primary fatty amines.

Quaternized polyvinyl pyridine.

Polyvinyl pyridine.

Alkyl quaternary ammonium halide.

Typical compound drogenacetate.

Dodecyl dimethyl amine hydrogen phosphate.

Ethylated ,lauryl carbamyl .guanidine.

Dimethyl hexadecyl amine.

Stearyl hetrocyclic ethyl amine.

Tetradecyl dimethyl amine oxide.

Lauryl diethanol amide.

Dodecyl ethoxylated amine.

Polyvinyl pyridine polymethyl chloride.

Polyvinyl pyridine, mo-

lecular weight 40,000 to400,000.

Cetyl trimethyl ammonium chloride.

Olyl dimethyl amino hy- 7 Class of cationic substances:

Alkyl aryl quaternary ammonium halide.

Hydroxy ethyl alkyl imidazo lines.

Amine esters of long chain fatty acids.

Substituted amide of alkyl 7 phosphate. 7

Quaternized alkyl polyvinyl pyridinium.

Polymerized ethylene imine.

Typical compound Dimethyl benzyl cetyl ammonium chloride. Heptadecanyl (1) hydroxyl ethyl (2) alkyl imidazoline. Stearyl amidoacetate trimethyl chloride. Dodecyl imine phosphate ester. Polyvinyl pyridinium methyl chloride. Polyethylene imine (average mol. weight The following examples are illustrative of the compositions and processes of the present invention, but it is to be understood that the invention is not to be limited to the specific details thereof:

EXAMPLE I This example illustrates the co-deposition of an inorganic phosphate-anionic polymeric coating followed by cationic insolubilization of the anionic polymer to form an adherent co-polyrner wherein the following typical bathsand processing steps are employed.

Bath 0. 1

Material component: Weight percent Sodium acid pyrophosphate 1.0 Water 91.5 Polymeric vinyl toluene sulfonic acid (molecular weight, 400,000) 1.0

Zinc oxide 1.0

Orthophosphoric acid (75%) 5.0

Nitric acid (60%) 0.5

Bath N0. 2

Material component: Weight percent 2-hydroxyethyl heptadecanyl 2-imidazoline 1.0

- Orthophosphoric acid (75 0.5

Ammonium hydroxide (28%) 0.5

Water 98.0

The following variations in concentrations (percent by weight) may be observed in bath No. 1: sodium acid pyrophosphate, 0.6-2.0; water 97.0-85.0; vinyl toluene sulionic acid, 0.55-1.60; Zinc oxide 0.5-2.0; orthophosphoric acid 3.0-7.0; nitric acid, 0.25-0.85. The following variations in concentrations (percent by weight) may be observed in bath No. 2: imidazoline,.0.72-l.8; orthophosphoric acid, 0.0-1.5; ammonium hydroxide, 0.03l.2; water 9925-960 The pH of bath 1 was 2.0 and the pH of bath 2 was 6.0. Ranges of 2.0-2.8 and 5.8-8.5, respectively, may be utilized. Application of these baths was as follows: Descaledhot rolled steel or cleaned cold roll steel of the low carbon series in the form of sheet was heated to 140 F. andconveyed at speeds of 200 ft. per

minute through applicator rolls which were flooded with a composition corresponding to bath No. 1. The excess of bath No. l was squeegeed off by passing through a set of squeegee rolls. The reaction with the steel was allowed to proceed for an interval of about 20 seconds.

Then the strip or sheet is passed through another set of applicator rolls flooded with solution corresponding to bath No. 2 to form the insoluble copolymer. This was followed by a pass through squeegee rolls to remove the excess reactants, followed by a water rinse. The work was then dried in warm air at 200 F. The steel was thus rendered preserved for storage and/ or application of organic finish. The reaction taking place between the mono- 3,136,663 mer group of the anionic polymer and the cationic reagent is illustrated as follows:

Both baths and the metal are maintained at a temperature of about 125 F. during the application cycle.

Vinyl toluene sulfonic acid Heptadecanyl imidazoline NC Hg CHgCHg-- HC-CH -C=CH O17H3E C 0 3) 416113 3) e a 2) N Hz i l ('n O=T=O O=$=O 0: =0 Hg OH OH [1 H I H;

CHrCHg HC-CHz --CH=CH2 Ca s a) a s 9 n s( i) CHn-lfil H2 IfiICHg (.LAH2IIICO "H C 11H35C-II\ICHZ C17H35C-NJJHQ CH CH Hg I Hg H; I H3 OH 0H 11 DE A similar reaction occurs when the cationic reagent is EXAMPLE 3 A similar bath produces a desirable finished coating which provides protection of galvanized steel strip from Polyvinyl toluene ammonium sulfonate Dodeeyl methyl benlzlyl taimethyl ammonium c on e the formation of white rust and simultaneously prepares it for painting.

EXAMPLE 2 In the treatment of phosphatized steel, zinc or cadmium coated steel, it has been found that unpainted corrosion behavior is improved with the embodiment of a minor Material component: Weight percent Polyvinyl styrene sulfonic acid (molecular but effective amount of a molybdate such as ammonium Weight 350,000) 1.0 molybdate, sodium molybdate, ferro molybdate 01' Z c Ammonium molybdate 0.25

molybdate. A typical bath for this purpose has the fol- ,Phenyl glycol ether 0.5

lowing composition. Zinc carbonate 0.25

Water 98.0

Material component: Weight percent Y Y toluene Sulfonlc acld (molecular The ingredients may be varied in concentration (weight Welght 400,000) percent) as follows: vinyl styrene sulfonic acid, 0.5-2.5;

Zinc carbonate ammonium molybdate 0.1-0.5; phenyl glycol ether, 0.0-

Ammonium molybdate 1.0; zinc carbonate, 0.0-0.5; Water 99.2-99.5. The pH Of Phytic acid (70%) this bath was adjusted to 6.8 using orthophosphoric acid. Orthophosphoric acid (75%) A plication was by roll on at 140 F. and was followed Water by a subsequent roll-on application of the cationic reagent The following variations in concentrations (percent with final dry-off in warm air. The cationic reagent bath by weight) may be utilized; vinyl toluene sulfonic acid, had the following composition. 0.5-2.5; zinc carbonate, 0.1-0.5; ammonium molybdate, 0.1-0.5; phytic acid, 0.0-0.2; orthophosphoric acid, 0.0- 05; water 99.3-95.8. The pH of this bath was 6.0 (it Material component: Weight percent Dodecyl methyl benzyl trimethyl ammonium hloride 1.0 can be ad usted to the range of 5.0-6.8 with ammonium C hydroxide or orthophosphoric acid as requir Aft f g 2;? application to the zinc strip by roller-coating, the metal ga OSP one am (7 0) 9 received a subsequent treatment with the cationic reagent of Example 1, also by roll on application. The meta The following variations in the ingredients of the was rinsed with water and then dried with warm air. ationi reagent bath a b ob d; quaternary mmonium compound 0.-2.0; ammonium hydroxide, 0.0 0.1; orthophosphoric acid, 0.00.l; water 99.5-97.7. The

pH of this bath was 6.0 (it can be adjusted to the range of 5.0 to 8.1 using ammonium hydroide or. orthophosphoric acid as may be required).

EXAMPLE 4 Another example of treatment for the preservation of galvanized steel sheet is disclosed as follows.

Material component: Weight percent Polyvinyl sulfonic acid (molecular weight 1,200,000) 1.0 Ammonium molybdate 1.0 Calcium hydroxide 0.25 Ammonium hydroxide (28% 0.1 Water 97.65

The following variations in concentration (percent by weight) may be observed: polyvinyl sulfonic acid, 0.75-

2.5; ammonium molybdate, 0.25-15; calcium hydroxide 0.0-0.5; ammonium hydroxide, 0.0-0.25; water, 98.9- 95.25. The pH of this bath was 5.5 (it can be adjusted to 5.0-6.5 using ammonium hydroxide or orthophosphoric acid as may be required). The cationic reagent bath had the following composition.

Material component: Weight percent .Cetyl trimethyl ammonium chloride 2.0 Orthophosphoric acid (75%) 0.1 Water 97.9

The following variations in concentrations (weight percent) can be utilized: cetyl trimethyl ammonium chloride, 0.52.5; orthophosphoric acid, 0.10.25; water, 99.4- 93.25. The pH was 6.0 (it can be adjusted in the range of 5.58,3 using ammonium hydroxide or orthophos phoric acid as may be required).

It is possible to reverse the treatment steps and still secure desirable preservation of metal surfaces. This can be accomplished by first treating the metal or the conversion coated metal with the cationic reagent in monomeric or polymeric form and then reacting it with the anionic reagent in monomeric or polymeric form. preferred to use the sequence of first treating with the anionic polymer since cationic substances frequently exhibit a passivating action on the metal surfaces and thereby reduce their ability to enter into a subsequent reaction. It is further possible to utilize the anionic polymers and cationic reagents in the treatment of phosphatized steel, zinc, cadmium and other disclosed metals and alloys by conventional immersion or spray wash treatments.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details set It is' forth, but my invention is of the full scope of the appended claims.

I claim:

1. A process for the preservation of metal surfaces comprising the steps of applying to such surfaces an acidic aqueous solution containing an amount of a watersoluble inorganic component selected from the group consisting of compounds of phosphorous, compound of molybdenum and mixtures thereof, said component being reactive with said metal to provide a corrosion-resistant coating thereon and a minor proportion of an anionic metal reactive synthetic organic polymer derived from an unsaturated monomer capable of polymeric reaction, followed by the application to such surfaces of an aqueous solution containing a minor proportion of an organic cationic substance having a basic nitrogen atom effective to react with said anionic polymer.

2. The process of claim 1 wherein the anionic polymer has the generic formula:

where R' is an organic group with a free valence capable of polymeric reaction, X is a strong polar group selected from the group consisting of a sulfonic acid group, a carboxylic acid group and a .phosphonic acid group; Y is selected from the group consisting of hydrogen, an ammonium radical and a metal, A is a hydrocarbon terminal group and n is an integer greater than one.

3. The process of claim 2 wherein the anionic polymer is selected from the group consisting of polystyrene sulfonic acid, ammonium and metal salts of polystyrene sulfonic acid, polyvinyl toluene sulfonic acid and ammonium and metal salts thereof, polystyrene phosphonic acid and ammonium and metalsalts thereof, polyvinyl phosphonic acid and ammonium and metal salts thereof, methylacrylic acid polymers, co-polymers and salts thereof, hetero-maleic acid polymers of styrene and salts thereof, and polyvinyl sulfonic acid and salts thereof.

4. The process of claim 2 wherein the aqueous solution containing an anionic polymer includes phytic acid.

5 The process of claim 4 wherein the inorganic component includes a phosphate.

6. The process of claim 1 wherein the inorganic ponent includes a phosphate.

7. The process of claim 1 wherein the inorganic ponent includes orthophosphoric acid.

8. The process of claim 7 wherein the inorganic ponent includes a molybdate.

9. The process of claim 1 wherein ponent includes a molybdate.

10. The process of claim 1 wherein the anionic mer comprises polyvinyl toluene sulfonic acid.

11. The process of claim 1 wherein the anionic polymer and the cationic substance are each present in said solutions in amounts within the range 0.5 to 2.5% by weight.

12. The process of claim 1 wherein the anionic polymer comprises polyvinyl toluene sulfonic acid and the cationic substance comprises a quaternary ammonium compound.

13. The process of claim 12 wherein the inorganic component includes a phosphate.

14. A process for the preservation of metal surfaces comprising the steps of applying to said surfaces an acidic aqueous solution containing an amount of a watersoluble inorganic component selected from the group consisting of compounds of phosphorous, compound of molybdenum and mixtures thereof, said component being reactive with said metal to provide a corrosion-resistant coating thereon and a minor proportion of an anionic metal-reactive synthetic organic polymer derived from an unsaturated monomer capable of polymeric reaction having a substituent selected from the group consisting of a sulfonic acid group, a phosphonic acid group, a Carcomcom-

com-

the inorganic boxylic acid group and salts of said acid groups followed by the application to said surfaces of an aqueous soiution containing a minor proportion of an organic cationic substance having a basic nitrogen atom, said cationic substance being reactive with said anionic polymer.

15. An article of manufacture comprising a basis metal having a protective coating comprising the reaction product, in situ on the surface of said basis metal, of a water-soluble inorganic component selected from the group consisting of compounds of phosphorous, compounds of molybdenum and mixtures thereof, said com ponent being reactive with 'said metal to provide a corrosion-resistant coating thereon and an anionic metal.

reactive synthetic organic polymer derived from an unsaturated monomer capable of polymeric reaction having a substituent selected from the group consisting of a sulfonic acid group, a phosphonic acid group, a carboxylic acid group and salts of said acid groups with a cationic substance containing a basic nitrogen atom.

(References on following page) UNITED STATES PATENTS Snyder et a1 May 15, 1951 Wilson et a1. Aug. 14, 1951 Kempthorne July 7, 1953 Schuster et a1 Mar. 27, 1956 16 McLaughlin Oct. 2, 1956 McDonald May 5, 1959 Wooding May 19, 1959 FOREIGN PATENTS Great Britain Feb. 15, 1946 

1. A PROCESS FOR THE PRESERVATION OF METAL SURFACES COMPRISING THE STEPS OF APPLYING TO SUCH SURFACES AN ACIDIC AQUEOUS SOLUTION CONTAINING AN AMOUNT OF A WATERSOLUBLE INORGANIC COMPONENT SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS OF PHOSPHOROUS, COMPOUNDS OF MOLYBDENUM AND MIXTURES THEREOF SAID COMPONENT BEING REACTIVE WITH SAID METAL TO PROVIDE A CORROSION-RESISTANT COATING THEREON AND A MINOR PORTION OF ANANIONIC METAL REACTIVE SYNTHETIC ORGANIC POLYMER DERIVED FROM AN UNSATURATED MONOMER CAPABLE OF POLYMERIC REACTION, FOLLOWED BY THE APPLICATION OF SUCH SURFACES OF AN AQUEOUS SOLUTION CONTAINING A MINOR PROPORTION OF AN ORGANIC CATIONIC SUBSTANCE HAVING A BASIC NITROGEN ATOM EFFECTIVE TO REACT WITH SAID ANIONIC POLYMER. 